The overall aim of this submission is to examine if cognitive functioning in MCI can be improved with training exercises. These findings could further our understanding about the mechanisms of MCI, inform our attempts to intervene in this disease, and influence the design and methodology of future clinical trials. We propose a randomized, placebo-controlled, clinical trial using [230] older adults with MCI. Following pre-testing with a cognitive battery, participants will be randomly assigned to either the experimental group or an active control group. Those in the experimental group will complete 40 1-hour sessions of online, computerized exercises designed to improve processing speed and auditory memory (Brain Plasticity, Inc.). Those in the control group will complete 40 1-hour sessions of online, computerized activities that are not specifically designed to improve cognition (e.g., crossword puzzles). Post-testing will follow completion of training in both groups. We will also examine effects of the training program after 12 months. By achieving these aims, we expect to advance our understanding of the mechanisms and treatment of MCI, which will have effects for clinical care and research. For example, if these individuals do benefit from cognitive training, then this may reduce the disability associated with this disease. This project is consistent with the mission of the National Institute on Aging. Relevance. Minimizing the deleterious effects of MCI is critical for providing clinical care and advancing research with this disease. For example, if cognitive deficits can be minimized, then individuals may retain functional independence for longer periods of time. Similarly, awareness of factors that moderate the effects of intervention will allow us to target individuals for future clinical trials in MCI.